Thermal flex contact carriers  #2

ABSTRACT

The present invention relates generally to permanent interconnections between electronic devices, such as integrated circuit packages, chips, wafers and printed circuit boards or substrates, or similar electronic devices. More particularly it relates to high-density electronic devices. The invention describes means and methods that can be used to counteract the undesirable effects of thermal cycling and thermal fluctuations. The invention more specifically shows certain improvements related to its mother patent application, called Thermal Flex Contact Carrier (TFCC), where the improvements allow the height of the contact elements to be now not restricted anymore by the size of the spaces or distances between the contact pads of the devices to be attached together. Certain improvements to the carrier wafer are also shown.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a NON-PROVISIONAL UTILITY patent application, andshould be considered as a DIVISIONAL or a CONTINUATION or aCONTINUATION-IN-PART patent application, based on patent applicationSer. No. 12/154,753, FILED May 27, 2008, TITLE “TFCC™ & SWCC™ THERMALFLEX CONTACT CARRIERS”, which is a CONTINUATION patent application,based on patent application Ser. No. 11/689,558, filed Mar. 22, 2007,title “NO-WICK™ 2 INTERCONNECTIONS”, now U.S. Pat. No. 7,901,995 issuedMar. 8, 2011, title “Interconnections Resistant To Wicking”, which is aDivisional patent application based on patent application Ser. No.10/937,647, filed Sep. 8, 2004, title “INTERCONNECTIONS”, now U.S. Pat.No. 7,196,402 issued Mar. 27, 2007, which in turn is a DIVISIONAL patentapplication, based on patent application Ser. No. 10/075,060, filed Mar.17, 2003, title “INTERCONNECTIONS”, now U.S. Pat. No. 6,884,707, issuedApr. 26, 2005.

This application is claiming the priority and benefits of the followingprior applications, which include the same references, which wereclaimed by the mother applications. These prior applications are thefollowing eight patent applications, where three are provisional patentapplications and four non-provisional utility patent applications, allof which are incorporated herein in their entirety by reference:

1) Provisional Patent Application Ser. No. 60/231,387, filed Sep. 8,2000, entitled “Probers”, which will be referred to as Ref1, and

2) Provisional Patent Application Ser. No. 60/257,673, filed Dec. 22,2000, entitled “Probes and Sockets”, which will be referred to as Ref2,and

3) Provisional Patent Application Ser. No. 60/268,467, filed Feb. 12,2001, entitled “Probes, Sockets, Packages & Columns”, which will bereferred to as Ref3, and

4) Non-Provisional Utility patent application Ser. No. 09/947,240, filedSep. 5, 2001, entitled “Interconnection Devices”, which will be referredto as Ref4.

5) Non-Provisional Utility patent application Ser. No. 10/075,060, filedMar. 17, 2003, entitled “Interconnections”, which will be referred to asRef5. This application has been granted the U.S. Pat. No. 6,884,707 B1,issued Apr. 26, 2005.

6) Non-Provisional Utility Patent Application Ser. No. 10/937,647, filedSep. 8, 2004, title “Interconnections”, now U.S. Pat. No. 7,196,402issued Mar. 27, 2007, which will be referred to as Ref6.

7) Non-Provisional Utility patent application Ser. No. 11/689,558, filedon Mar. 22, 2007, entitled “NO-WICK™ 2 INTERCONNECTIONS”, now U.S. Pat.No. 7,901,995 issued Mar. 8, 2011, title “Interconnections Resistant ToWicking” , which will be referred to as Ref7.

8) Non-Provisional Utility patent application Ser. No. 12/154,753, FILEDMay 27, 2008, TITLE “TFCC™ & SWCC™ THERMAL FLEX CONTACT CARRIERS”, whichwill be referred to as Ref8, or simply as TFCC1.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

PREFACE OR EXECUTIVE SUMMARY

In the following specification, I will do something which may beconsidered non-traditional.

First, I will refer to the mother application, Ref8, as TFCC1, forshort, for ease of referencing it. And, I will refer to the presentapplication, as TFCC2, for short.

Then, I will copy and/or paraphrase a good amount of the specificationof the mother application, TFCC1, and will even use some of the figuresof TFCC1. I will use this portion of the present specification tohighlight the weaknesses of TFCC1 and where it needs certainimprovements.

Then, I will concentrate on TFCC2 and will describe the new concepts,which are being introduced by this present application, TFCC2, toovercome these TFCC1 weaknesses

This way, it will be easier for the reader, to understand the basis orstarting points from TFCC1, and to appreciate the value of theimprovements offered by TFCC2.

I hope that this approach will be acceptable.

DEFINITIONS

For the purpose of the following invention description, I will usecertain words or terms that may be peculiar to this application. Theywill be explained in the following definitions, or as I go along duringthe application.

-   Barb=Detent-   Carrier=Carrier Wafer-   Contact=Contact Element, which usually comprises a head, a stem and    sometimes, a foot.-   Foot=Contact bottom flap, which would be soldered to the PCB for    example. As mentioned in TFCC1, the foot may be optional. We may    have instances where the foot is eliminated, and the contact side    view will look like an inverted letter “ELL”.-   Head=Contact top flap, which would be soldered to the BGA for    example-   Lance=Contact Stem, Leg, Column, Lead-   Solder Mask Any coating or surface treatment, which would render the    material, to which it is applied, non-solderable or non-wettable to    the joining material being used in the attachment process.-   TFC Thermal Flex Contact-   TFCC Thermal Flex Contact Carrier-   wrt=with respect to-   Warp As per Webster: (Weaving) the threads running lengthwise in the    loom.-   Weft or Woof As per Webster: (Weaving) the yarns carried back and    forth across the warp. From Wikipedia: In weaving, weft or woof is    the yarn which is drawn through the warp yarns to create a fabric.    In North America, it is sometimes referred to as the “fill” or the    “filling yarn”.-   Standard Integrated Circuit Packages:-   LCCC: Leadless Ceramic Chip Carrier-   BGA: Ball Grid Array Package-   PCB: Printed Circuit Board-   PGAP: Pin Grid Array Package-   SIP: Single In-Line Package

Please refer to other definitions in Ref5 and Ref6 and Ref8, the latterbeing referred to also as TFCC1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to high-density interconnections betweenelectronic devices and components.

The invention relates more specifically to what is referred to as“permanent” interconnections, which include solderable interconnections,and/or mounting of electronic components on boards or on substrates, oron other electronic components and the like.

It provides interconnection elements, called contacts or legs or lead orcolumns, to such components and it covers the shapes and orientation ofthese leads, to enhance the performance and reliability of suchcomponents, especially when these components are part of electronicsystems that are exposed to harsh environment, such as temperaturecycling and fluctuation.

The present invention covers in particular interconnections between“lead-less” electronic components and boards and/or substrates, orbetween similar lead-less components.

The specification utilizes many of the definitions and items describedin the referenced earlier patent applications.

2. General Background and Prior Art

In the case of leadless electronic components, like the BGAs and theLCCCs, it has been known that soldering such components directly tosubstrates or to PCBs can create certain problems. It can lead topremature failure of the interconnecting joints. This is especiallytrue, when the component is relatively large, i.e. approx. ½ inch orlarger on the side, and when the material of the component is differentthan that of the substrate, e.g. when the component is silicon orceramic, while the substrate is FR4, and when the temperature can varyconsiderably during the operating life of the assembly.

The problem results mostly from exposing electronic assemblies tovarying temperatures, such as thermal cycling or power cycling, orsimply from being exposed to harsh environment, including hot and coldtemperature environment. This is especially true, when the component isrelatively large, when the material of the component is different thanthat of the substrate, and with different TCEs, i.e. where TCE Mismatchexists between the assembled devices, and when the temperaturefluctuates considerably and frequently during the life of the assembly.

For this reason, several designs have been proposed in the past tocounteract the unfavorable effect of such conditions. For example, theinventor, Gabe Cherian, together with other co-inventors, had invented,back around 1982, what was called “CCMD”, Chip Carrier Mounting Device,which was later called “Solder Quick” or “Solder Columns” or “CherianColumns”. This is covered by U.S. Pat. Nos. 4,664,309, 4,705,205 and4,712,721. Other attempts have been made by other inventors, which weremore or less successful. And finally, the inventor came up with theNo-Wick™ concept mentioned in the Refs.

The additional problem nowadays is the fact that many of the componentsare being miniaturized. The center distances between contact pads aregetting smaller and smaller, and some of the old inventions can nolonger keep up with such miniaturization. For example, BGAs have centerdistances down to 0.020″ (approx. 0.5 mm) or less, and when we considerChip Scale Packaging, the center distances can be even smaller. TheCherian Solder Columns were originally designed and built to work with0.050″ (approx. 1.25 mm) center distances. Cherian Solder Columns cannotreadily be simply scaled down to size. For this reason, Cherian createdthe No-Wick™ concept mentioned in the Refs. Then, both Don Saunders andGabe Cherian created the TFCC and the SWCC inventions described in Ref8,the TFCC1. Now, again, both Don Saunders and Gabe Cherian created thispresent invention, the TFCC2, as a Continuation to TFCC1, which will bedescribed in the present patent application here below.

PRIOR ART

There is a lot of prior art in this field. Several designs have beenproposed in the past to counteract the unfavorable effect of the abovementioned conditions.

In the “mother” patent applications, which are referenced above, I havelisted a few important prior art documents. Please refer to them.

OBJECT & PURPOSE OF THE INVENTION

The purpose of this present invention, TFCC2, is to improve on some ofthe features of the mother invention, TFCC1, while keeping many of theoriginal features of TFCC1. This will be done by adding a few newfeatures, for the purpose of improving and enhancing the usefulness ofthe inventions.

So for now, I will repeat and paraphrase the text of the purpose of themother invention, TFCC1, and consider it to be the purpose of bothinventions, i.e. of both TFCC1 and TFCC2, and then at the end, I willadd and describe the special purpose of TFCC2.

The purpose of both inventions, TFCC1 and TFCC2, is to solve theproblems resulting from exposing electronic assemblies to varyingtemperatures, such as thermal cycling or power cycling, or simply frombeing exposed to harsh environment, including hot and cold temperatureenvironment and especially if there is a TCE mismatch between the joinedcomponents.

The general object of the two inventions is to introduce certain changesand/or improvements in the way Integrated Circuit (IC) Packages known asBGAs, Ball Grid Array Packages and other similar leadless devices andchips, and assemblies that incorporate such packages and/or chips, sothat assemblies made out of such devices would become more reliable andcan better withstand the above mentioned undesirable effects of thermalcycling and power cycling and thermal fluctuations.

Another object of the two inventions is to provide means to reliablymount leadless electronic packages or components, such as a BGA onPrinted Circuit Boards (PCBs), or chips on substrates, especially towithstand any undesirable effect of TCE Mismatch and the effects ofThermal Cycling and/or Power Cycling.

A further object of the two inventions is to provide improvedinterconnections and mounting means for Integrated Circuit Chips andPackages, to make such assemblies more reliable and to better withstandstresses induced by thermal effects and/or by shock and vibrations.

These mounting means include providing “contacts or legs or leads orcolumns” between the chip or the package and their carrying base, i.e. aPCB or the like, to provide a “buffer” zone, where the columns would actas flexible joints, to absorb these undesirable effect of TCE Mismatch,and/or effects of Thermal Cycling and/or Power Cycling.

Another object of both inventions is to accomplish all the above,especially for High-Density devices, i.e. devices with small centerdistances between their contact points.

A corollary result is that we can convert any “leadless” package ordevice to become a “leaded” one. So for example, a leadless BGA wouldbecome similar to a Pin Grid Array Package.

In addition to all that, is the fact that we do all this in a way, suchas to control the flow of solder along the stem of the columns, so as tomaintain the flexibility of the columns.

Yet another object is to reinforce the assembly against severe shock andvibrations, by providing an “anchor” between the components of theassembly.

Now, One last, but not least, special object of the present invention,TFCC2, is to improve on the TFCC1, by providing new designs and methodsof construction, so as to attain longer, taller, higher leads betweenthe devices to be attached and assembled together, and consequently tofurther improve the reliability and the thermal cycling life of suchassemblies.

The summary of the main goals and the advantages of the proposed changesand improvements of this present invention, TFCC2, is to provide leads,that are taller, and more slender and flexible than can be provided byTFCC1, and to make these leads more yielding, thus requiring less forceto hold them in place at their anchor points in the body of the package.This translates itself into a situation, where the solderjoints/interconnections between the devices would be less stressed, thusless apt to crack or break, so as to reduce the occurrence of thoseundesirable solder joint failures, thus prolonging the life of theelectronic systems which contain these chips, packages and the like. Inshort, this translates into improving the reliability of the electronicassemblies and systems. A corollary resulting advantage is that theinterconnections between the package and the substrates would lastlonger and the whole system would be more reliable and last longer aswell.

But back to the special purpose of TFCC2. TFCC2's main purpose is toprovide new construction designs, which will result in obtaining leads,which are taller, larger, higher than the leads that can generally beobtained by TFCC1, and hence the TFCC2 leads will be more flexible thanthe TFCC1 leads, and hence they would provide a longer thermal Cyclelife and more reliable assemblies than with TFCC1.

One Additional Benefit With Shock and Vibrations

This was covered in TFCC1, but I am trying to explain it here a littlebit better. If we look at a standard DIP package, we notice that theleads are in two rows of leads, where the leads are all orientedorthogonally in the same direction. If the package is subjected to shockor vibrations that are concentrated in a certain direction, then thepackage will withstand the resulting stresses, depending on the relationbetween the direction of the shock and vibration and the direction ofthe leads and the natural resonance frequency of the device, in thedirection of the induced/forcing vibration. This is because thestiffness of the leads is high if we stress the device across the edgesof the lead, and the stiffness is low across the face of the leads. Wecan say also that the resonance of the device will be different,depending on the direction of the shock and/or vibration, applied on it.So, if the direction of the shock and vibration is in a generallyfavorable direction with respect to the direction of the leads, then thepackage will withstand the stresses well. On the other hand, if thestresses are in an unfavorable direction, then the package may fail.

However, if the leads were oriented as per the present invention, wheredifferent leads would have different angles with respect to the axes ofthe package or device, then the stiffness of the leads would be moreevenly distributed, and the package may fare better regardless of whichdirection the shock and vibrations are coming from.

This is roughly what I was trying to show by the sketch in Ref3, pagePP-D-106.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1, which is the Prior Art-TFCC1-FIG. 2-A, explains the basics ofthe whole TFCC concept.

FIG. 2, which is the Prior Art-TFCC1-FIG. 20-B, shows a view of theTFCC, by itself and making it clear that the contact are created out ofone single sheet of conductive metal.

FIG. 3, which is Prior Art-TFCC1-FIG. 45, shows a pattern of contacts,showing some details of the contact blanks and their pattern ofdistribution and orientation for a device that has ten concentric rowsof contact pads, and it shows also the moats and the etching around the“pads”, where the legs length “L” is 0.635 mm.

FIG. 4, which is Prior Art-TFCC1-FIG. 48, shows a close up view of thetop three rows of contacts shown in FIG. 3, and the “angles” of theoriented contacts, A9, B9, C9, D9, and E9, from Row 9 of FIG. 3 andhighlights the areas where the contact blanks do interfere with eachother.

FIG. 5, which is Prior Art-TFCC1-FIG. 49, also shows a close up view ofthe top three rows of contacts and the arrangement with a new angle,which prevents the interference between the contact blanks, which waspresent in FIG. 4.

FIG. 6, which is Prior Art-TFCC1-FIG. 43, shows a view of half theprofile of two adjacent contacts arranged in a row and in line, oneafter the other and their relative dimensions.

FIGS. 7 and 8, which are Prior Art-TFCC1-FIG. 44-A and 44-B, show astudy of the relation between the pitch, the pad diameter, the width ofthe moat, and the left-over length of the leg.

FIG. 9, which is Prior Art-TFCC1-FIG. 50, shows a configuration ofcontacts for a device, which has only one peripheral row of contactpads. The leg dimension L is 0.635 mm for a pitch of 0.80 mm. Similar toL1 in the previous FIG. 6.

FIG. 10, which is Prior Art-TFCC1-FIG. 51, shows an example, where theleg length was increased from 0.635 mm to 1.00 mm, just for illustrationpurposes.

FIG. 11, which is Prior Art-TFCC1-FIG. 52, shows the case where thedevice has two peripheral rows of contact pads. Again, the leg dimensionL is the same, i.e. 0.635 mm for a pitch of 0.80 mm.

FIG. 12, which is Prior Art-TFCC1-FIG. 53, shows an almost similararrangement of two peripheral rows, as in FIG. 11, which is PriorArt-TFCC1-FIG. 52. The only difference is that the length of thecontacts was also increased, as in FIG. 10, from 0.635 mm to 1.00 mm,just for illustration purposes, to gain more flexibility.

FIG. 13 shows the germ of the idea that created TFCC2. We put twoportions of devices like the ones shown in FIG. 10 or 12, concentricallyone inside the other, to create TFCC2s, which could have much longertaller leads than with TFCC1.

FIGS. 14 through 18 show details about examples of TFCC2s, based on theconcept shown in FIG. 13.

FIG. 19 shows a strip of carrier, where single contacts are beinginserted in it. In FIG. 19-A the contacts are all in the same direction(orthogonal), while in FIG. 19-B, the contacts are “oriented”.

FIG. 20 shows how strips like the ones shown in FIG. 19 can be stackedone next to the other, to create a slab, as in FIG. 20-C, with thecontact leads arranged in a matrix, to match the corresponding device tobe attached to. The strips can be made as a one single row arrangementeach, as in FIG. 20-A, or can be made as a double row arrangement each,as in FIG. 20-B. Again, more rows can be accommodated in one singlestrip, as desired.

FIG. 21 shows details of how the “foot” of the contact can be formed.

FIG. 22 shows details of how the contacts can be “blanked” out of acontinuous Leadframe and stitched into a carrier wafer. The contacts canbe stitched to be “orthogonal” or “oriented”.

FIG. 23-A shows an ISO view of a contact, which has “barbs”, to ensurethat it will be more securely retained into the carrier wafer. FIG. 23-Bshows a bottom view of the contact, highlighting the fact that the footcould be made slightly narrower than the stem.

FIG. 24 shows an ISO view and an end view of a contact that is beingformed into a ZEE or an ESS shape, so as to impart to it the capabilityof flexing in the Z-direction, in addition to flexing in the X- andY-directions.

FIG. 25 shows another contact being formed into a “CEE” shape, also toimpart to it, the capability of flexing in the Z-direction.

FIGS. 26 and 27 show a few slightly different variations of theembodiments shown in FIGS. 19 through 23.

FIG. 28 shows some different details as to how we can form the wirecontacts shown in FIGS. 26 and 27.

FIG. 29 shows three different ways we can make and form the contactelements, especially if we want the stem to flex more at the middle ofthe height of the stem.

FIG. 30 shows how the contacts shown in FIG. 28 could be attached to aBGA. It highlights at least two important points. One, that the contactsare oriented as per present invention. Two, that the “belly” of thecontact is pointing inwards, which makes it easier to form.

FIGS. 31-A and 31-B show a carrier wafer, as per Prior Art TFCC1, whichcould be used in this TFCC2 invention.

THE PROBLEMS OF TFCC1, THAT WE WANT TO SOLVE BY INTRODUCING TFCC2

The problem or weakness with the mother invention, TFCC1, is the resultof the way it is manufactured. One of the TFCC1 goals and objectives wasto make the device as economically as possible. So in one of the majorembodiments of TFCC1, we decided to carve out all the contacts out ofone single sheet of conductive metal. But as a result, we became limitedor rather restricted as to how tall or high we can make thecontacts/legs/leads/columns.

I will first describe the original TFCC1 and how it is made, to clarifythe reason why it is limiting or restrictive, and then will describe theimprovement, which will be introduced and provided by TFCC2. Thissequence in the description will make it easier to understand andappreciate what the improvements are.

Description of the Features and Method of Manufacturing of the MotherInvention, TFCC1

TFCC1 introduced the concept of the thermal flex contacts as shown inFIG. 1, which is the Prior Art-TFCC1-FIG. 2-A. TFCC1 allows forattaching each one of such contact to the leadless device, such as aBGA, although the preference would most probably be to try to attachmore than one contact at the same time. So, this is why TFCC1 went alsoin the direction of the embodiment shown in FIG. 2, which is the PriorArt-TFCC1-FIG. 20-B.

This FIG. 2 shows how one of the major embodiments of the TFCC1 is made.The main feature is that a large number of thecontacts/legs/leads/columns are produced out of one “blank” sheet ofconductive metal, and the individual contacts stay attached to thatsheet until they are attached to the devices that they are intended towork with ultimately. This makes it easier and more economical to createand to handle the contacts and to go through the manufacturing and thefinal assembly processes.

An additional feature is that we can “orient” the leads in a way toreduce their resistance to bending, thus improving even further theireffectiveness in reducing the stresses on the solder joints andprolonging the operating life of the assemblies and the electronicsystems.

The third feature of the invention is to “CONTROL” the solder flow alongthe column, so as to ensure that there will still be some amount offlexibility in the column, after all the soldering/joining operationshave been completed.

Specific Features of TFCC1, Which Will Relate To TFCC2

I will now describe the features of TFCC1, which will be improved byTFCC2 FIG. 2, which is Prior Art-TFCC1-FIG. 20-B, shows that theindividual contacts are carved out from one flat sheet of metal, whichwe will to as the base metal sheet.

FIG. 3, which is Prior Art-TFCC1-FIG. 45, shows a pattern of contacts,where the legs length “L” has been chosen to be increased by 0.1 mm, sothat L became 0.635 mm as per FIG. 6, for a standard pitch of 0.8 mm anda BGA pad diameter of 0.33 mm, i.e. R1=0.165 mm in This is the longestcontact blank that we can attain for this pitch, as described below inFIG. 6, which is Prior Art-TFCC1-FIG. 43.

We see that there is interference between some of the contacts, asexplained below.

I will skip the description of TFCC1-FIGS. 46 and 47 of FTCC1, becausebasically they lead to what is shown in FTCC1-48 and 49, which areTFCC2-FIGS. 9 and 10 in this application.

FIG. 4, which is Prior Art-TFCC1-FIG. 48, shows the same view as in FIG.3, which is Prior Art-TFCC1-FIG. 45, but it also shows the “angles” ofthe oriented contacts, A9, B9, C9, D9, and E9, which are the contactblanks in the row #9 of the matrix. Obviously, the angle A1 of the A9contact is “zero”, because the contact is in line with the center line.We can see that the angle E1 of the E9 contact makes it such that the E9contact does not interfere with the E10 contact. So, if we couldre-orient all the contacts that are interfering, so they would beoriented at a similar angle like that of E9 contact, then we would behome free!

FIG. 5, which is Prior Art-TFCC1-FIG. 49, shows the arrangement with thenew angle. All the 4 contacts, which were interfering with the contactsabove them, have been re-oriented to have a same angle like the angle E1in FIG. 4. Now, we see that there is no interference any more.

This angle applies only to this row of contacts. For the other rows, amore appropriate angle can be found, using a similar approach as we haveused for the row just described.

This angle would control the orientation angle of the contact after ithas been fully formed.

Of course, ideally we would like to have each and every contact orientedwith the ideal/theoretical ray, which start at the thermal center,usually the geometric center of the device and ends at the center of therespective contact pad. This would provide the least resistance tobending from the contact body. However, if we deviate from this idealorientation by a small amount, we may still be OK. It is a trade-offbetween the orientation of the leg and the length of the leg. We canactually calculate the stresses on the leg and the solder joints, oreven do a Finite Element Analysis (FEA), and determine the effect of theangle or the length of the leg on the stresses in the whole picture,i.e. on the individual elements of the joints. This way, we can evaluatethe benefits or the downfall of re-orienting the contacts, or not tore-orient them.

FIG. 6, which is Prior Art-TFCC1-FIG. 43, shows a study of the essentialdimensions of the contact blanks, along one of the central axes, wherethe space available for the contact blanks is at a minimum. P, the pitchbetween the contact pads of the devices to be assembled, controls thespace available for the contact blanks. M is the width of the moat andit is controlled by the manufacturing process, which is used to createthe moat. The rest of the dimensions are clearly illustrated in thefigure.

The best scenario is if we let the contact blanks run into each other asshown in the right hand side blank. Its tip, F, is running into thesolder ball pad, H, of the left hand blank. Here, I will copy orparaphrase the TFCC1 description of FIG. 43 through.

FIG. 6, which is Prior Art-TFCC1-FIG. 43, shows a view of half theprofile of two adjacent contacts arranged in a row and in line, oneafter the other. This arrangement would give us the “tightest” or“smallest” room/space to create the contacts. This will also give us thedimensions of all the other contact blanks in the whole matrix, becausethe contacts should all have the same length. The dimensions wereselected to accommodate a BGA with a pitch of 0.8 mm for this example.Since the moat width, M, is governed by the manufacturing process, andassuming that we will remove metal, say by chemically milling the moator by a laser or stamping operation, then we have opted to make the moatapproximately about 0.1 mm wide.

The contact ref #4301 on the left hand side of the figure shows a moat4311 all around it. The remaining material inside the moat can bevisualized to make the three major portions of the contact. First is the“Head” 4321 with a length H, which would provide the area to be joinedto the BGA pad. Second, the “Foot” 4323, with a length F, provides thearea to be joined to the substrate pad. Lastly, the “Stem” 4325, with alength S1, which will be the “column” between the Head and the Foot. Thegrooves 4327 and 4329 are optional features, to facilitate the bendingprocess. The pitch “P”, which is the distance between the centers of thecontact pads governs and controls the space available to provide thethree major portions of the leg.

As can be seen from left hand side contact in the drawing and from theconfiguration of the contacts, the length L1 of the “leg” measured fromthe center of the “pad” turned out to be 0.533 mm, for a pitch of 0.8 mmand using a BGA contact pad diameter of 0.33 mm.

If we try to make L any longer, then either the moat need to be narroweror the leg would push the moat to encroach on the space of the pad.

If we use a “lancing” operation, where no metal is removed, asillustrated in the right hand side contact 4303 of FIG. 6, which isPrior Art-TFCC1-FIG. 43, then we would not need a moat, which was 0.10mm wide, at the end 4331 of the contact. This way, we could increase thelength “L” of the contact by that same distance, namely by 0.1 mm.

Hence the length “L2” will become 0.6350 mm.

FIGS. 7 and 8, which are Prior Art-TFCC1-FIGS. 44-A and 44-B, show astudy of the relation between the pitch, ref #4411, the pad diameter,ref #4413, the width, ref #4415, of the moat, ref #4437, and theleft-over length, ref #4417, of the leg. The total length, ref #4431, ofthe leg, ref #4433, will provide the pad, ref #4435, the two necks, ref#4421 and ref #4423, the stem, ref #4425, and the flat bottom, ref#4427.

Ideally, we want the stem, ref #4425, to be as long as possible.

Also, ideally, we want to have a sizeable flat bottom, ref #4427,

But, if the dimensions are not cooperating, we can think of at least twoalternatives, used either separately or together.

First, we could eliminate the “flat bottom”, ref #4427, of the leg. Notvery desirable, but conceivable/doable. It could work OK, but it couldcreate some problems.

The second alternative is explained below, and it is to force the length“L”, or S1 or S2 in FIG. 6, which is Prior Art-TFCC1-FIG. 43, to belarger, but how? This is not easy with the general TFCC1 approach.

Now, we will get to four embodiments which will lead the way to ourTFCC2 invention.

FIG. 9, which is Prior Art-TFCC1-FIG. 50, shows a configuration ofcontacts for a device, which has only one peripheral row of contactpads. Here, the contacts are shown to be oriented, as best desired forstress reduction. Attaching the TFCC would basically convert a leadlessdevice to a leaded device.

Obviously in this case, the length of the contact legs can be increasedwithout any restrictions, other than the question of space or the heightof the device on top of the PCB, for example. FIG. 10, which is PriorArt-TFCC1-FIG. 51, shows such an example, where the leg length wasincreased from 0.635 mm to 1.00 mm, just for illustration purposes. Ofcourse, it can be made longer.

FIG. 11, which is Prior Art-TFCC1-FIG. 52, shows the case where thedevice has two peripheral rows of contact pads. Here, the contacts werearranged so that the outer row of contacts would start pointingoutwards, while the contacts of the inside row would start pointinginwards. Of course, after they get bent to have their legs perpendicularto the body of the TFCC, the legs would align properly and their ends,which will be soldered to the PCB, will be located properly at theircorrect respective positions.

FIG. 12, which is Prior Art-TFCC1-FIG. 53, shows an almost similararrangement of two peripheral rows, as FIG. 11, which is PriorArt-TFCC1-FIG. 52. The only difference is that the length of thecontacts was increased, to gain more flexibility. Again, in such a case,there is hardly any limit as to how much you can increase the length ofthe leg, as explained above.

Please keep in mind what was just said about the four embodiments shownin FIG. 9, which is Prior Art-TFCC1-FIG. 50, through FIG. 12, which isPrior Art-TFCC1-FIG. 53. This will be the starting point for the TFCC2concepts described in this present invention.

Summary of the Present TFCC2 Invention Concepts and ObjectivesA—Inventions Concepts and Objectives, Common to Both TFCC1 and TFCC2

Provide a “Flexible Leads” device, to interconnect electronic devicestogether. We call this device, TFCC, Thermal Flex Contact Carrier, andit would provide flex contacts, or legs or leads or columns if you will,to leadless IC devices, such as BGAs or chips or the like, at one end ofthe TFCC leads, and to Printed Circuit Boards (PCBs) or substrates orthe like, at the other end. These TFCC leads would in essence convertleadless devices into leaded ones.

Make the contacts as long, tall, slender columns, instead of shortstubby solder joints.

Make the contact with an elongated or rectangular cross section. Thiswill make the leads more flexible when bent on their flat, more so thanif they would be bent on edge.

Place the contacts/leads with elongated or rectangular cross-sections,in an orientation or direction, such that the more flexible section ofeach leads column would be in the direction of the largest expectedthermal expansion or contraction. This translates into orienting thefaces, so that the flat wide surfaces of each individual column will befacing towards its respective expected thermal center or the fixationpoint of the assembled components or the assembly, so as to minimize thestresses during the expected thermal cycling or thermal fluctuations.

B—Inventions Concepts and Objectives, Specific to TFCC1

Create all the contacts out of one sheet of conductive material, so asto make the end product as economical as possible.

C—Inventions Concepts and Objectives, Specific to TFCC2

Find ways to increase the length/height of the contacts, so that theywill provide more flexibility to the joints between the attacheddevices, and consequently increase/improve the reliability and thermalcycling life of the assemblies.

Use Carrier Wafers, which can double up as solder mask as well.

Shape the contact leads, so that they would have “weaker” bendingportion(s), to facilitate bending and/or flexing.

Make the contact elements out of plain wires or flat sheet metal, andshape them in a special way, to have a “weaker” bending resistance atcertain locations along the length of the leads.

Description of the Present Invention, TFCC2, and Its Embodiments andDrawings Summary and Purpose of the Present TFCC2 Invention

As explained above, the mother invention, the TFCC1, has one majorweakness or shortcoming. Basically, the length or height of the leadsthat the TFCC1 can provide is limited and restricted and may not give usas much flexibility as we may need or as we may like to have. We areconstrained by the layout of the contact pads of the devices to beassembled, by the distance between these pads, whether in the directionof the orthogonal axes or in the direction of the expected thermaldeformations. This was explained in more details, earlier above.

It is desirable to extend the length or height of these leads, so as toincrease their flexibility, and to consequently improve/enhance thereliability and thermal cycling life of the assembled devices and of theassemblies in general.

The purpose of this present invention, TFCC2, is to provide solutions,which will allow us to do just that, i.e. to provide longer tallerhigher leads.

Several solutions will be presented, all of which basically solve theproblem of the length or height of the leads, in one way or another.

In addition, I am re-introducing some features of the wafer carrier,such as using it to double up as a solder mask element, and adding oneor two new features to it as well.

Some TFCC1 Features that We Would Like to Preserve

TFCC1 also adopted the original basic concept of the No-Wick™, Ref xxx,which is to control the flow of solder, so that the solder stays atand/or near the joints between the column ends and the electroniccomponents. The solder should not flow away from the column ends, andshould not migrate and stick to the stem of the column. If it does, thenthe column will become thicker and less flexible. If this happens, thenwe would reduce the benefits of having slender and flexible columns asthe connecting element, and we could go back and have premature failuresof such assemblies. So, this No-Wick™ concept has been incorporated inthe above TFCC1 invention and will be retained and included in thepresent TFCC2 inventions as well.

An additional feature is to have the columns curvilinear.

Usually most columns are straight and generally perpendicular to thedevices. We will refer to the general direction of the columns as theZ-direction or the Z-axis. We will refer to the general direction(plane) of the devices as the X- and Y-directions. This would includethe whole plane of the devices, which is usually generally flat. Thecolumns Z-direction is generally perpendicular to the device's X- andY-directions. The straight columns will provide relief and flexibilityin the direction that is perpendicular to their axis, which in this caseis in the X-direction or the Y-direction or both; but not in thevertical direction, i.e. not the Z-direction. As a result, relativelylarge assemblies may have the tendency to warp out of flat under severethermal conditions. This condition could be compared to that of abi-metal strip that would bend or curl, under varying temperatureconditions.

But if the columns are curvilinear, ever so slightly, they may providesome flexibility along their general Z-axis as well, which would begenerally perpendicular to the components. This would reduce thistendency of the devices and/or the assembly to warp out of flat.

However, since the center distances are small, and space is tight, wecannot have the columns curved haphazardly. They would either take toomuch space, or if we try to place them closer to each other, they maytouch and short. So, the suggested solution is to have the columns“parallel nested” and to have their curves and shapes such that theywould allow such parallel nesting. (See Ref4 for more details on thesubject of parallel nesting).

One more feature to preserve is the concept of the “anchor”, whichreinforces the assembly and protects it against severe shock andvibrations.

Description of the Preferred Embodiments of the Present Invention, TFCC2

While the invention is susceptible of various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but, on the contrary, theinvention is to cover all modifications, alternative constructions andequivalents, falling within the spirit and scope of the invention asdefined in the claims.

While I am describing the drawing in more details, I will at the sametime explain the technology basis of the invention. I will also includea number of examples in this section, which should be considered as partof the embodiments for the purpose of this application as well.

This description covers more than one invention. The inventions arebased partly on the same technology platform, but then each of theinventions embodiments has some additional features of its own. Notbeing an expert in handling patents, I would like to leave it to thepatent examiner to decide on the number of the inventions contained andhow to split one invention from the other. Also, to decide which can beconsidered as Divisional application, or a Continuation-In-Part, orrather as regular Continuation.

BRIEF DESCRIPTION OF DRAWINGS

A brief description of the TFCC2 drawings,

FIGS. 13 through 29 or XXX, was given already earlier above. Pleasereview them at that location. FIGS. 1 through 12 were also included inthe above Brief Description of the Drawings, but they covered thefeatures of the mother invention, TFCC1, which we are trying to solvehere now.

DETAILED DESCRIPTION OF THE DRAWINGS AND OF THE PREFERRED EMBODIMENTSFirst Preferred Embodiment Interposed Sets of Double or SinglePeripheral Contacts

FIGS. 13 through 18.

FIG. 13 shows a rough concept of the basic idea of the first embodiment.It shows two concentric parts, part 1 and part 2, one “interposed”inside one other. Each one of these two parts can be extracted orexcised from a TFCC1, such as those described in FIGS. 9 through 12. Wecould refer to either of them as a TFCC2 Contact Annular. And dependingon it size, we can give a size number as well.

Because the length of the leads in these special TFCC1s is notrestricted by the pitch, i.e. by the spaces between the contact pads ofthe devices to be attached together, whether the orthogonal distances orotherwise, then we can make the leads as long as we want. This wasexplained also earlier above, when FIGS. 9 through 12 were described. Ofcourse, we should increase the leads' length, within reason. I mean, wedo not want to make the leads so long as to have an excessive heightbetween the attached devices, because this may make the assemblies toohigh, too large for the available spaces.

I will explain this basic concept in more details in the following FIGS.14 through 18.

FIG. 14 shows a TFCC2 Contact Annular, which was extracted from theTFCC1 shown in FIG. 12. If we take the TFCC1 of FIG. 12 and fold thecontact blanks so that the stems will be generally perpendicular to thegenerally flat body of the TFCC1, and if we cut out excessive portionsof the flat base sheet, or the carrier, from the inside area and fromthe outside area which included the registration tabs etc, then we wouldend up with a TFCC2 Contact Annular, that would look like the one shownin FIG. 14.

Let's look at FIG. 12 again. The rows are identified by numbers that runfrom number 1 at the central horizontal axis, and going out to number 2,3, etc. The two rows of contacts in this FIG. 14 are rows number 9 and10. So, we can refer to this TFCC1, in FIG. 12, as a TFCC1 “9-10”.Consequently, we will refer to the TFCC2 Contact Annular, which wasderived from it, and which is shown in FIG. 14, as the TFCC2 ContactAnnular “9-10” or simply TFCC2 “9-10”.

Now, let us visualize that we make another TFCC1, like the one in FIG.12, again with two concentric rows of contacts, but for a device thathas only two concentric rows of contact pads, for only the two rowsnumber 7 and 8. We would refer to this TFCC1, as a TFCC1 “7-8”. Now, ifwe extract from it a new TFCC2 Contact Annular, it would look like theone shown in FIG. 15. Logically, we would refer to this one as a TFCC2“7-8”.

Now, we can repeat the process and create a TFCC2 Contact Annular withonly the two rows number 5 and 6, like the one shown in FIG. 16. Wewould refer to this one as the TFCC2 “5-6”.

And so on.

Now, let's visualize that we have a BGA, which has only four rows ofcontact pads, which are located at rows number 5, 6, 9 and 10, skippingrows number 7 and 8. We could take one TFCC2 “5-6” as in FIG. 16, andtake one TFCC2 “9-10” as in FIG. 14, and join them by some means, tocombine them and to create one that looks as in FIG. 17. We would referto this one as a TFCC2 “5-6-9-10”.

We can go on and create all kinds of combinations of TFCC2, by simplycreating TFCC1s, as needed and by combining them in a similar fashion.

For example, we can create the TFCC2 “5 6 7 8 9 10”, as shown in FIG.18, by simply repeating the process described above.

If necessary, we can create a TFCC2 Contact Annular with only one row,by excising it from a TFCC1 like in FIG. 10, for example.

Now, as to how we would join these various segments of TFCC2s together.

We can visualize a number of ways to do that. For example, we can mountall the various excised segments on a temporary common base, either atthe BGA end or at the PCB end, then we “glue” the segments together, andthen once the segments are joined together, then the temporary commonbase can be removed if so desired or if necessary, or otherwise thattemporary common base can stay in place as part of the TFCC2 endproduct. For example, this temporary common base can be made of a sheetof solder mask material, and can be place on the stem side of thecontacts, leaving the side of the contacts that will adjacent to the BGAunencumbered. Another way is that the annulars can be held together by aremovable/dissolvable or stay-in-place skin, either above or below theshown surfaces, or in between the annulars.

I am sure that a person skilled in this art can find other ways, aswell, to hold the various excised segments together.

Second Preferred Embodiment Individual Strips With Contact Elements

FIGS. 19 through 21 show the main concepts of the Second Embodiment,with some variations thereof.

FIG. 19 shows a strip of carrier wafer 192, which carries one single rowof contact “pins”. The individual contact pins can be prepared inadvance and then inserted into the strip, one at a time, or severalcontacts at a time. Again, a person skilled in this art can come up withmore that one way to accomplish this insertion task.

FIG. 19-A shows that the contacts have been lined up, so that all ofthem will be in the same direction or orientation. I refer to thisarrangement as “orthogonal”. The pitch would match the pitch of therespective devices that will use these contacts, and the length of thestem can be whatever we want it to be.

Then we can lay several such strips, side by side, as in FIG. 20-C, tocreate the desired matrix to match the BGA or any such device.

FIG. 19-B, the lower view in this figure, shows a similar arrangement,except that now, we have oriented the contact lances, according to themother and the present invention, i.e. “so that they present the leastresistance to bending/flexing in the expected respective direction ofthe thermal deformation of the respective devices to be attached bythese contact pins.”

Of course, in this case, the degree of orientation, or rather the angleof each individual contact will be based on the respective position orlocation of that individual contact, with respect to the whole matrix ofcontacts of the receiving device, such as a BGA for example. In otherwords, if the strip shown in FIG. 19-B is intended to create the row #9in a device like the one of FIG. 14, then the orientation angles of theindividual contact would match the orientation angles shown for thecontacts in row #9 of that device in FIG. 14. But if the strip shown inFIG. 19-B will create the row #10 of that device of FIG. 14, then theorientation angles of the individual contact would be slightlydifferent. The angles will be selected to match the angles of thecontacts in row #10 of that device in FIG. 14, and the strip will beidentified as such, i.e. each strip will be identified as to whichlocation it belongs to in the specific matrix. This will be repeated asnecessary, so that when the individual strips will be joined side byside, as in FIG. 20-C, then all the contacts will be oriented properly.

Let me repeat. We can prepare individual strips, which will ultimatelybe arranged side by side, as in FIG. 20-C, to form a matrix as neededfor the respective device to be assembled, similar to the arrangementmentioned above, but with an important difference. Here the individualcontact lances will be oriented , such that each one of the contactleads will be oriented in its individual respective direction, whichwill coincide with the ray from the thermal center, or fixation point,of the device, going to the face of the individual respective contactlance, so that every such individual lance will be oriented as perpresent invention, i.e. “so that it would present the least resistanceto bending/flexing in the expected respective direction of the thermaldeformation of the respective devices to be attached by these pins.”

Another feature shown in FIG. 20 is the solder foot, which will beattached to the second device, e.g. a PCB.

FIG. 20-A shows a similar strip, similar to the one in FIG. 19-A, withthe contact lances all oriented in one direction, i.e. orthogonal, butwhere the PCB end of the contacts have been bent/folded, so as to createa foot, to facilitate the soldering of the lead to the PCB pads, forexample.

FIG. 20-B shows two such strips, side by side, or a “dual row” strip.The feet of the individual contacts can be bent/folded first and thenthe strips would be placed side by side, or the feet can be foldedafterwards. Also, you can notice that the feet in FIG. 20-B are pointingtowards each other, i.e. the folds are in opposite directions. This isan option. The second option is to bend all the feet to point in thesame similar direction, which could be easier to manufacture and tohandle. The third option is to “orient” the feet as per presentinvention. In this case, it would make sense to orient the wholecontact, including the lance of the contact, as per present invention,and simply fold the feet so they become oriented automatically.

FIG. 20-C shows several such strips placed side by side, to create aTFCC, i.e. a slab of TFCs. The individual strips will be joined togetherto create a matrix of contacts, which would correspond and match thematrix of contact pads of the devices to be assembled.

FIG. 21 shows one possible method for fabricating and forming the solderfeet of the contact elements, to create the feet which will be solderedto a PCB or a substrate. Shown are the clamps, which can act such thatone clamp would apply pressure or simply acts as a mechanical stop,while the other clamp at the opposite side of the lance would act as theanvil. Then a third movable member can act as the pusher slide to foldthe foot as desired. The pusher can have a smooth rounded front cornerto facilitate the folding operation.

FIG. 21-A shows an isometric view of a strip 211, with a number ofcontacts 221 inserted in it. The lower tip of the contact at the lefthand end of the strip is being folded to create the foot of the leadwhich will be soldered to the PCB or the substrate.

FIG. 21-B shows an end view of the parts involved.

Also the Press 214 and Anvil 215 can be shaped, as in FIG. 10-C, suchthat they can “trap” the contact lance and have a better control on itsposition during the folding operation.

The contacts can be folded one at a time, or more than one contact canbe folded at the same time. Again, a person skilled in the art canfigure out how to do all that.

Third Preferred Embodiment Carrier Wafer With Contact Elements

FIGS. 22 through 25 show the main concepts of the Third Embodiment, withsome variations thereof.

FIG. 22 shows a carrier wafer that can be populated with TFCC contactelements, by stitching, i.e. by inserting the contact elements/lancesinto the wafer. It is a different way of creating the interconnectiondevice. Here, we will be using contact elements, similar to those usedin the TFCCs, but we will have them prepared individually and theninsert them into a carrier, to end up looking as shown in FIG. 22.

The individual contacts, contact elements, can be prepared in advanceand/or can be made out of a strip of conductive metal 221 as shown,which I will call the leadframe. The contacts 223 can be etched orstamped out of the leadframe, and can be held on to the leadframe byappropriate tabs, basically in a way like many other contact spring orcontact elements are made which are used for sockets and connectors. Orthe contact elements can be shaped on the fly, i.e. during the stitchingoperation, e.g. stamped out of the full strip of conductive material.The leadframe strip can be prepared so as to have a certain area of it,already coated by a layer of solder mask 222, along a “band”, whichultimately would create the stem portion of the contact elements.Individual contact elements 225 will be cut out from the leadframe andthe stem will bent at 90 degrees wrt the head and then inserted into thecarrier.

A by-product of this approach is that the contact will end up with anelongated cross section, where the thickness of the base metal of thestrip is much smaller than the width of the contacts. This will make thecontact leads more flexible when bent on their flat, more so than ifthey would be bent on edge.

A stitching machine, almost like a sewing machine or a stapling gun, cantake the contact element and insert its lance/stem in the carrier wafer.The contact lances can be arranged on/in the carrier wafer in a matrixthat would match the matrix of the BGA/device, in pitch anddistribution.

In a way, this could be the same procedure that could be used to createthe strips shown in FIGS. 19, 20 and 21. Also the feet of the leads inFIG. 22 could be bent in a similar way as shown in FIG. 21.

The stitching operation can be done by several methods.

Stitching method #1: One is to keep hold of the carrier wafer in oneposition and move the stitching head from one point to the next to fillthe whole matrix of pins in the carrier wafer. The leadframe providingthe individual contact elements can be located at a steady/fixedlocation and the stitching head can go to the leadframe and grab onecontact element at a time and then move to the proper location at thecarrier wafer and insert the lance/lead there, and then go back to theleadframe and grab the second contact element and repeat the process.

Stitching method #2: Another method is to provide the leadframe/strip asan attachment to the stitching head and would move with the stitchinghead from one insertion point to the next.

Stitching method #3: A third option is to keep the stitching head in onelocation and move the carrier wafer back and forth and from side toside. This would look more and more like a sewing machine, where thethread and the stitching head/needle are in one location and where thecloth is moved right and left and to and fro, with respect to thestitching head, to accomplish the sewing operation.

Please notice that we can see in FIG. 22 that the contacts in thecarrier, carrier [wafer] wafers 226 and 228, are shown in two differentgroups. The [left hand side of the] carrier 226 is populated by contactsthat are placed all in the same direction, which I will refer to as an“orthogonal” matrix, while the 228 [right hand side] shows that thecontacts are “oriented each one in a special direction”.

This can be seen more clearly, if we look at the pin directions 227 and229. The pin directions 227 are all parallel to each other, which meansthat the cross section of the pins lances or stems are all parallel toeach other and in the same direction. This is an example of theORTHOGONAL arrangement. On the other hand, the pin directions 229 aredifferent. Each one of the direction of the various pins is pointing ina different direction. But they all are oriented in a way, such thatthey will all converge, generally, at one single predetermined point,which generally is the thermal center of the device and/or of theassembly of the device attached together. The point of convergence canalso be a fixation point related to the device or the assembly. This isan example of the ORIENTED arrangement.

The oriented contacts will be oriented as per the present invention,i.e. such that the more flexible section of each leads column would bein the direction of the largest expected thermal expansion orcontraction. This translates into orienting the faces, so that the flatwide surfaces of each individual column will be facing towards therespective expected thermal center or the fixation point of theassembled components or the assembly, so as to minimize the stressesduring the expected thermal cycling or thermal fluctuations.

So, the contact elements could be arranged in an orthogonal fashion, asin the carrier 226 [left hand side half of the matrix] shown in FIG. 22,or in an “oriented” fashion, as in the [the RHS half of] the carrier228.

In order to accomplish the arrangement [of the RHS of the FIG. 11] shownin the lower figure of FIG. 22, i.e. as in the carrier 228, with thepins oriented as per pin directions 229, again we can consider thefollowing few options.

Stitching Method #4:

We keep the stitching head and the contact leadframe all in one“permanent” location and “orientation” as in Stitching Method #3, andmove the carrier wafer in the X- and Y-directions and at the same time,rotate it in an angle “A”, as shown in the lower figure of FIG. 22, sothat the contact lances will ultimately be oriented as needed as perpresent invention.

Stitching Method #5:

We can keep the carrier wafer stationary and move the stitching head inthe x and y direction and at the same time, rotate it in a specificangle, to position the respective lance at the appropriate respectiveangle, as per present invention.

Preferred Embodiment #4

FIG. 23 shows a couple of additional enhancements. (1) Enhancement #1: Apre-coined contact, which that snaps into (2) Enhancement #1; a moldedor excised carrier of various thicknesses.

The preformed or pre-coined contact looks similar to what is shown inFIGS. 19 and 21, but shows a few variations. It has two staked barbs 235just below the round head 231, at a distance from the pad head whichdepends on the thickness of the isolative carrier. The carrier, like 192or 194 in FIG. 19, can be molded and can also have a rectangular openingfor the foot of the contact to enable a straight-in insertion of thecontact. The orientation is defined by the molding and the leg slotkeeps the contact held vertical and locked in the molding. Automatedcontact tooling and insertion can be enabled to fabricate both thecontact and the carrier to defined lengths and orientations and pitches.

An excised carrier can also be used, which can be made by a simple lasercutting out of a plastic material, like sheeting or thicker substrates.

Few additional explanatory details. First, FIG. 23 shows that the PadHead 231 is round, so as to more closely match the size of the solderball on a BGA and to provide a good solder joint at this end of thecontact. Second, it does highlight the fact that the contact lead orstem 233 or lance has an elongated/rectangular cross section. Third, itshows some “barbs” 235 are staked into the sides of the stem, to act asdetents, to hold/retain the contact element more securely into thecarrier (not shown) in this FIG. 23, but similar to the carriers inprevious figures). Fourth, it shows [in FIG. 23 B,] that the foot 237 ofthe contact element is slightly narrower [that] than the width of thestem. This makes it that the carrier opening would allow the contact tobe pushed through the carrier and then the leg or stem will snap inplace and the barbs will retain the contact in place.

Notes:

1—Use of Adhesives:

Please refer to FIGS. 26 and 27. In all the above embodiments, if wefind it necessary and beneficial, we could also apply some adhesivematerial 275 between the top of the carrier 261 and the bottom of thepad head, or between the carrier and portion of the stem that will beretained inside in the carrier, to ensure a better retention.

Another way to ensure that the contacts will stay in place, especiallywhen using a carrier wafer that is receptive to this proposed method, isto apply some heat and/or pressure to the head of the contact element,so that it sticks to the material of the carrier wafer.

2. Foot: The foot, which is the Contact bottom flap, which would besoldered to the PCB for example. As mentioned in TFCC1, the foot may beoptional. We may have instances where the foot is eliminated, and thecontact side view will look like an inverted letter “ELL”.

3. Anchor: We should keep in mind that we can still incorporate the“anchor” in any of the present invention's embodiments.

Embodiment #5

We talked earlier about the flexibility of the contacts in theZ-direction. In some cases, this could be a beneficial/desirablefeature. FIGS. 24 and 25 show two examples of contacts that wouldprovide some flexibility in the Z-direction. FIG. [24] 24-A shows anisometric view of a contact, with a curvilinear profile, as seen in theend view. FIG. 24-B, which could be referred to as a ZEE-shape or anESS-shape. [[It]] FIG. 24-B also shows the tooling that could be used tocreate such a profile. FIG. 25 shows another variation on the profile.We could call this a CEE-profile. The tooling is slightly different thatthe one in FIG. 24. I am sure any person skilled in this art can findvarious other ways to accomplish the desired end result.

Embodiment #6

FIGS. 26 and 27 show another variation as to how to make and prepare andpresent the contact elements to the “stitching machine”, if you will,which will insert them into the carrier. First of all, FIG. 26 showsthat the contacts can be made out of regular wire, made of a conductivematerial, say copper. The most economical way is to use a “round” wire,but wires with other cross-sections could be considered as well. Wecould also use wires made out of a springy material, such as BerylliumCopper, if we feel that it would enhance the performance. But thematerial needs to be solderable, if we want to use solder as the joiningmaterial.

FIG. 26 shows that the wires are carried by two paper strips 261 orcould be double strips. This could be similar to the way some resistorsor circuit protection devices that are carried on a bandolier, forexample. Then the portion of the wire which will create the stem portionof the contact can be treated to become non-wettable to the joiningmaterial. If it is solder, then we could apply a solder masking coating.Then we could use a “spanking” or “coining” operation, at variouslocations along the wire, to create the flat/round pad head 262, whichwe call the BGA flap, and to create a certain bulging portion, as 271 inFIG. 27, to act as the detent, to simulate the “barbs” 235 of FIG. 23.We could even create another flat portion, to simulate the foot 263 and273 in FIG. 27 of the contact, which we call the PCB flap or the PCBfoot. Then the individual wires, which by now would look pretty muchlike the etched or stamped leadframe leads, would be [picket] picked outof the bandolier and inserted into the carrier 265, by a method similarto the ones mentioned earlier above or any equivalent method.

FIG. 27 shows an enlarged view of the contact of FIG. 26, sitting in thecarrier. The foot 273 is shown before and after it is bent. The bendingcan be done after the insertion, in a similar way as was mentionedearlier above in connection with FIGS. 20 through 25.

FIG. 28 shows some different details as to how we can form the wirecontacts shown in FIGS. 26 and 27. Configuration 7 in FIG. 28 shows anadditional bend, near the middle of the stem height, to simulate theeffect of the curvilinear shapes in FIGS. 24 and 25, i.e. to increasethe flexibility in the vertical Z-direction. It is also the shape of thecontacts, that are shown in FIG. 30.

FIG. 29, actually the three figures in FIGS. 29-1, 29-B and 29-C, show[shows] three different ways we can make and form the contact elements,especially if we want the stem to flex more at the middle of the heightof the stem. The [LHS] contact in FIG. 29-A shows an hour glass stem,the [middle] contact in FIG. 29-B shows a notch near the center of thestem height, and the [RHS] contact in FIG. 29-C shows a “Necking” nearthe middle of its stem height.

FIG. 30 shows how the contacts shown in FIG. 28 could be attached to aBGA. It highlights at least two important points. One, that the contactsare oriented as per present invention. Two, that the “belly” of thecontact is pointing inwards, which makes it easier to form.

The Carrier Wafer

The carrier wafer can be made of a material that can be removed, ordissolved or disintegrated, after the assembly operation is completed,i.e. after attaching the BGA to the PCB for example.

Embodiment #7-A

We can use a material similar to the carrier material invented by GeoffWong et al, as in U.S. Pat. No. 4,655,382, Wong et al, “MATERIALS FORUSE IN FORMING ELECTRONIC INTERCONNECT”, which I refer to also as a“DISSOLVABLE CARRIES WAFER MATERIAL”. It is made out of a layeredconstruction, comprising layers of polymers and layers of paper. Thewafer is water soluble.

Once the reflow process is completed, we can remove the carrier wafermaterial, by putting it in a regular household kind of dishwasher andthe material will be simply washed away.

Embodiment #7-B Solder Masking Wafer Material

Here is another portion of TFCC1, which is important for this presentinvention TFCC2. FIGS. 31-A and 31-B, which are Prior Art-TFCC1-FIGS.68-A and 68-B, show a carrier that was made completely out of a soldermasking material, and then the contacts were inserted in it. We coulduse a similar material to make the carrier of FIG. 22, or any of theother carrier wafers or carrier strips, described by FIGS. 19 through21. In such a case, we would not need to prepare the contact elementswith solder masking, because the wafer material would perform the soldermasking function.

Embodiment #7-C Solder Masking Wong Carrier Wafer Material

I propose a new wafer material, in addition to those mentioned above andto those that are already in the prior art domain.

What I propose to achieve is basically to create a “composite” wafermaterial, made of a) the materials mentioned in the prior art, and b)some material that can act as a solder masking material, that would becombined inside the a-materials; so that the composite carrier waferwould act as “solder masking” as well.

We can visualize that if we combine the material of Geoff Wong togetherwith some of the material used in Embodiment #7-B, i.e. with a soldermasking material, then we would create an interesting new carrier wafermaterial.

I would call such a material, the “Solder Masking Wong Material” orsimply the SMW Material. With such a Solder Masking Wong Material”, wewould not need to prepare the contact elements with solder masking ofthe stem in advance.

This will be similar to the material of Embodiment #7-B, but would mostprobably be easier and faster to dissolve and/or remove.

We can combine the two materials in at least two different ways. One, wecan impregnate the compound used for the various layers with the maskingmaterial, or two, we can create a “layered carrier”, by simply apply themasking material on one or both sides of the standard Wong material.This can be in the form of a liquid that would get applied to theoutside surface of the Wong material, or in the form of a sheet materialthat can be laminated to it.

Embodiment #7-D TCE Controlled Carrier Wafer

This wafer material will have, in addition to the “standard” elements,or part of these standard elements that make the material, someingredients or additives which will control the Effective ThermalCoefficient of Expansion (TCE) of the material.

An example of such additives could be a set of “threads” which areembedded in the wafer material.

Note: This concept was already mentioned in Refxxx, towards the end ofthe specification. I am reviving the concept at this point, because itcan be very important, especially if the devices to be attached togetherare relatively large in the X- and Y-directions, in which case, thedifference between the Wafer TCE and the TCE of the devices can createproblems.

The purpose of the additives, whether they are in the forms of threadsor otherwise, would be to impart to the wafer a “Controlled TCE”.Controlled Thermal Coefficient of Expansion.

You see, with the Wong wafer material, the wafer has a TCE that islarger than the TCE of the ceramic packages. I think its TCE is evenlarger than that of FR4 boards. During the reflow process, the waferexpands more than the package, and consequently the contact elementsfollow the wafer and could get a bit out of alignment with their respcontact pads. When the solder is molten, the contact elements attach tothe BGA and to the substrate at the expanded position. When the totalassembly cools down and the solder starts to freeze, the wafer shrinksmore and the end result is some distortion in the shape and position ofthe solder and/or the contact elements.

In order to minimize this potentially undesirable effect, we need tofind a material for the wafer, which either has an inherent TCE thatmatches, as close as possible, the TCE of the package and/or the chip;or we need to “doctor” the “Actual/Effective/Apparent” TCE of the wafer,so that it does more closely match that TCE of the devices that will beattached together.

One way to achieve this goal is to “implant” in the wafer something toforce it to behave as if is has the desirable TCE or find a substitutematerial that has the desired TCE.

What I propose to achieve this goal is basically to create a “composite”wafer material made of a) the materials mentioned in the prior art,and/or b) some additives, for example some other polymer or powder orfibers, that would be compounded or dispersed or crisscrossed inside thea-materials; so that the effective TCE of the resulting material wouldhave a new TCE, which has a value close to the desired one, or againfind a substitute material that has the desired TCE.

Such fibers could be made out of fiberglass, or out of any othermaterials that have a small TCE or even a negative TCE. Ideally, thesefibers would have a “rough” outside surface so as to “grab” thesurrounding material and restrain it from sliding along the surfaces ofthe fibers.

Furthermore, it may be desirable to place these fibers, in the form of“threads”, as opposed to loose, bulk fibers or powder or granules.

A further improvement would be to place these threads in a crisscrossingpattern, pretty close to the way threads are woven together to make acloth, with the thread interwoven over and under the intersectingthreads. I believe they call this the Warp and the Weft. I will callthis the “Woven Pattern”.

A yet further improvement would be to lay the threads in separateindependent layers, whereby all the treads going in one direction, say,would lay in one level, while the threads perpendicular to the firstgroup would be laying in another layer, not over and under, i.e. not asa woven material, but simply be oriented and laying in one plane,separate from the other plane. I will call this the “Overlay Pattern.”

The purpose of the Non-Woven/Overlay pattern, but Oriented threadarrangement, is that we would be able to more easily pull the threadsout, after the reflow operation, if we wanted to. We would soak theassembly in an appropriate liquid to loosen up the thread, and then pullthese threads out.

If the threads are interlaced as in the Woven Pattern, it would be moredifficult to pull them out, even after soaking them and loosening them.

1. An improved TFCC, wherein the length of the stem of the contactelements is not restricted anymore by the spaces or distances betweenthe contact pads of the devices to be attached.
 2. A carrier waferwherein the body of the wafer which carries the contact elements candouble up as a solder mask as well.